Gray ratsnake

Location at the Zoo: Conservation Efforts

Region:

North America

Class:

Reptilia

Order:

Squamata

Family:

Colubridae

Genus:

Elaphe

Scientific Name:

Elaphe obsoleta spiloides

Description

:
The gray ratsnake is highly variable in colouration and pattern depending upon the age of the snake. Hatchlings have a pattern of dark grey or black blotches and spots over a background of light grey. As the snake ages, this pattern fades and the light grey darkens. Adults may be all black or black with some blotches visible. The chin and throat is white or cream coloured. The ventral colouration varies greatly from white to salmon to dark gray; a checkerboard pattern is typically present.

This is Ontarios largest snake. It reaches sexual maturity at an average length of 105 cm and can grow to 185 cm or more. At the widest point of the snake's body, its average diameter is four cm. The ratsnake is covered with keeled scales, and has a powerful slender body with a wedge-shaped head. The anal plate is divided.

Distribution

:
These snakes are widely distributed throughout the eastern and central United States, extending as far south as the Gulf of Mexico and as far north as southern Ontario in Canada. There are two widely separated populations in Ontario: the Carolinian in southwestern Ontario and the Frontenac Axis in southeastern Ontario. It is seen most often in the Kingston and Rideau Lakes areas.

Habitat

:
Although found in a variety of habitats, ranging from woodland to open field, farmland can provide ideal habitat for this species. They are found in old pastures, around farms or abandoned buildings, in quarries, in fields near open woodlands, and in residential areas.

The Frontenac Axis population in eastern Ontario occupies a variety of habitats including deciduous forests, wetlands, lakes, rocky outcrops and agricultural fields.

The Carolinian population in south west Ontario is found in a mix of agricultural land and deciduous forest, preferring habitat where forest meets more open environments.

Food

:
As the name implies, this species preys upon rats and other rodents. It also feeds on small birds (and their eggs) and other warm-blooded prey of suitable size.
Rat snakes in general are primarily known as rodent eaters; however other food preferences do exist. As juveniles, rat snakes eat small lizards, baby mice, and an occasional small frog. Adult rat snakes have a diet mainly consisting of mice and rats, but also include chipmunks, moles, and other small rodents. Rat snakes kill their larger prey by constriction.

Reproduction and Development

:
Between March and May, snakes begin to emerge from their winter hibernation. After a few weeks, they begin to seek out a mate, typically in late April, May, and early June. In Ontario the mating season runs from late May to mid-June. Males tend to wait for the females to pass through their territory, and with the use of pheromones, communicate and initiate the mating process with the female. Males attracted to the same female will engage in combat for the right to mate. The successful suitor approaches the female and flickers his tongue over her. He aligns his body with hers and attempts to wrap his tail around her tail with their vents nearly touching. Some males grasp the female with the mouth, to hold her in place and prevent her from moving away. The male then erects his hemipenes and inserts it into the female's cloaca while several small spines anchor the hemipenes firmly. Mating may last only a few minutes or span a few hours. During the breeding season, females will mate with multiple males and produce a clutch of eggs sired by different fathers.

In June or July, the female lays 10 to 20 oval eggs. The eggs are laid in a hidden area, under hollow logs, in the soft wood of rotting tree stumps or leaves, or in abandoned burrows. The eggs hatch 65 to 70 days later. The hatchlings are vigorous eaters and double their size rather quickly. If conditions are good, in the southern U.S. range, females sometimes produce two clutches of eggs a year.

Adaptations

:
The gray ratsnake is primarily active at night. It is both a terrestrial burrower and extremely good climber. It is found under rocks and boards, and in trees under bark and within knot holes and palm fronds. It will often move into barns and other outbuildings in June during the sparrow and swallow nesting season.

These snakes tend to be shy and, if possible, will avoid being confronted. If snakes are confronted by danger, they tend to freeze and remain motionless or they may hiss and flatten their necks in a menacing manner. Some adults attempt to further protect themselves. When threatened they will vibrate their tail. They coil their body and vibrate their tails in dead leaves which simulates the sound of a rattle. This may fool other animals into believing they are venomous. If the snakes continue to be provoked, they will strike. Ratsnakes may also produce a foul-smelling musk and release it on the predator if they are picked up, spreading the musk around with their tail. The musk acts as a deterrent. Ratsnakes are excellent swimmers.

Threats to Survival

:
Their habitat is slowly being reduced due to land development and the cutting of trees. Destruction of suitable hibernation sites can affect their survival. Since ratsnakes hibernate in groups at the same site each year, destruction of these sites heavily impacts local populations. Due to people's lack of knowledge and fear of snakes, rat snakes continue to be the victim of human persecution.